US11074936B2 - Magnetic disk device - Google Patents

Magnetic disk device Download PDF

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Publication number
US11074936B2
US11074936B2 US16/939,447 US202016939447A US11074936B2 US 11074936 B2 US11074936 B2 US 11074936B2 US 202016939447 A US202016939447 A US 202016939447A US 11074936 B2 US11074936 B2 US 11074936B2
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Prior art keywords
head
magnetic disk
magnetic
read
output
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US16/939,447
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US20210193178A1 (en
Inventor
Toru Watanabe
Takao Furuhashi
Akihiro Yamazaki
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Toshiba Corp
Toshiba Electronic Devices and Storage Corp
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Toshiba Corp
Toshiba Electronic Devices and Storage Corp
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Assigned to TOSHIBA ELECTRONIC DEVICES & STORAGE CORPORATION, KABUSHIKI KAISHA TOSHIBA reassignment TOSHIBA ELECTRONIC DEVICES & STORAGE CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: FURUHASHI, TAKAO, WATANABE, TORU, YAMAZAKI, AKIHIRO
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/60—Fluid-dynamic spacing of heads from record-carriers
    • G11B5/6005—Specially adapted for spacing from a rotating disc using a fluid cushion
    • G11B5/6011—Control of flying height
    • G11B5/607—Control of flying height using thermal means
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B19/00—Driving, starting, stopping record carriers not specifically of filamentary or web form, or of supports therefor; Control thereof; Control of operating function ; Driving both disc and head
    • G11B19/02—Control of operating function, e.g. switching from recording to reproducing
    • G11B19/14—Control of operating function, e.g. switching from recording to reproducing by sensing movement or position of head, e.g. means moving in correspondence with head movements
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/40—Protective measures on heads, e.g. against excessive temperature 
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/008—Recording on, or reproducing or erasing from, magnetic tapes, sheets, e.g. cards, or wires
    • G11B5/00813—Recording on, or reproducing or erasing from, magnetic tapes, sheets, e.g. cards, or wires magnetic tapes
    • G11B5/00878—Recording on, or reproducing or erasing from, magnetic tapes, sheets, e.g. cards, or wires magnetic tapes transducing different track configurations or formats on the same tape
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/127—Structure or manufacture of heads, e.g. inductive
    • G11B5/1278—Structure or manufacture of heads, e.g. inductive specially adapted for magnetisations perpendicular to the surface of the record carrier
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/60—Fluid-dynamic spacing of heads from record-carriers
    • G11B5/6005—Specially adapted for spacing from a rotating disc using a fluid cushion

Definitions

  • Embodiments described herein relate generally to a magnetic disk device.
  • a gap between a read head/write head and a magnetic disk should be decreased in order to improve the recording density, especially, track recording density of the magnetic disk.
  • There is a known technique to achieve the decrease of gap by providing a thermal actuator with the proximity of the read head/write head on a slider, and operating the read head/write head on the magnetic disk with a certain gap therebetween by the thermal actuator.
  • the present embodiment would present a magnetic disk device which can improve the recording density of the magnetic disk.
  • FIG. 1 is a schematic view of a technique of operating a head surface on a recording surface with a certain gap therebetween in a first embodiment.
  • FIG. 2 illustrates an example of a change in the gap between a head surface and a recording surface of a magnetic disk during one rotation of the magnetic disk of the first embodiment.
  • FIG. 3 is a block diagram indicative of an example of the structure of the magnetic disk device of the first embodiment.
  • FIG. 4 is a cross-sectional view of an example of the structure of a head of the first embodiment.
  • FIG. 5 is a schematic view illustrating a control to maintain a certain gap between the head surface and the recording surface of the magnetic disk of the first embodiment.
  • FIG. 6 illustrates an example of an output of a gap sensor in a case where there is a change in a floating degree of the head of the first embodiment.
  • FIG. 7 illustrates an example of the structure of a circuit configured to control a gap between the head surface and the recording surface of the magnetic disk of the first embodiment.
  • FIG. 8 illustrates an example of a result from adjustment of a control output value of a thermal actuator of the first embodiment.
  • FIG. 9 illustrates an example of the structure of a circuit to control a gap between a head surface and a recording surface of a magnetic disk in a second embodiment.
  • FIG. 10 illustrates an example of the structure of a circuit to control a gap between a head surface and a recording surface of a magnetic disk in a third embodiment.
  • FIG. 11 illustrates an example of the structure of a resistor in a case where several radius positions are set in the third embodiment.
  • a magnetic disk device includes a magnetic disk, a magnetic head including a read head to read data from the magnetic disk and a write head to write data to the magnetic disk, and a controller configured to control read/write from/to the magnetic disk by the magnetic head.
  • the magnetic head includes a thermal actuator configured to project a head surface of the magnetic head to a recording surface of the magnetic disk, and a detector configured to detect a gap between the head surface and the recording surface of the magnetic disk.
  • the controller controls a degree of projection of the magnetic head to the recording surface by the thermal actuator corresponding to the gap detected by the detector during the read/write.
  • thermal actuator hereinafter will be referred to as heater
  • heater a thermal actuator
  • FIG. 1 is a schematic view of a technique of operating a head surface on a recording surface with a certain gap therebetween.
  • FIG. 1 indicates a magnetic head slider (hereinafter will be referred to as slider) 301 , and a tip 301 A of the slider 301 is indicated in an enlarged manner in the part pointed by the arrow.
  • a magnetic head including a write head 303 and a read head 304 is disposed such that the head surface thereof faces the recording surface of the magnetic disk 305 .
  • a heater 302 is disposed in the proximity of the write head 303 and the read head 304 .
  • the heater 302 Upon application of a voltage to the heater 302 , the heater 302 is expanded, and the head surface of the write head 303 and the read head 304 is projected to the recording surface of the magnetic disk 305 , and thus, a gap between the head surface of the write head 303 and the read head 304 and the recording surface of the magnetic disk 305 is adjusted.
  • the head surface of the write head 303 and the read head 304 is detailed as an air bearing surface (ABS) 9 later with reference to FIG. 4 .
  • a degree of projection of the head surface of the write head 303 and the read head 304 is increased, the head surface is brought into contact with the recording surface of the magnetic disk 305 for once, a read signal and the like are referred to using a degree of projection at the contact as a reference, and the heater 302 is controlled such that a gap from the recording surface of the magnetic disk 305 becomes a desired degree.
  • FIG. 2 illustrates an example of changes between the head surface of the write head 303 and the recording surface of the magnetic disk 305 during one rotation of the magnetic disk 305 .
  • graph g 11 indicative of the recording surface of the magnetic disk 305 is not completely flat as depicted by straight line H.
  • the height of the magnetic disk 305 rotated by the spindle motor changes depending on the position of the slider 301 , and a radius of curvature of the magnetic disk 305 changes in one rotation.
  • the slider 301 is pushed onto the recording surface of the magnetic disk 305 by a suspension supporting the same with a constant weight, and when the magnetic disk 305 is rotated, a shear flow is generated in the air between the slider 301 and the magnetic disk 305 .
  • the air is pressurized such that the slider floats above the magnetic disk 305 with a certain gap therebetween.
  • a degree of floating depends on the height of the magnetic disk 305 directly below the slider 301 and the radius of curvature of the magnetic disk 305 .
  • a gap between graph g 12 indicative of a distance between the write head 303 and the recording surface and graph g 11 indicative of recording surface of the magnetic disk 305 changes within one rotation. That is, as compared to graph g 13 indicative of a constant gap, there will be a part where the gap increases and a part where the gap decreases.
  • a reference gap to operate the heater 302 is represented by a minimum gap D 11 of FIG. 2 , and thus, the average gap is derived as minimum gap+gap change/2.
  • FIG. 3 is a block diagram indicative of an example of the structure of a magnetic disk device 1 of a first embodiment.
  • the magnetic disk device 1 is, for example, a hard disk drive (HDD).
  • the magnetic disk device 1 includes a magnetic disk 2 , spindle motor (SPM) 3 , actuator 4 , voice coil motor (VCM) 5 , magnetic head (hereinafter will be referred to as head) 10 , head amplifier IC (head amplifier controller) 11 , R/W channel 12 , hard disk controller (HDC) 13 , microprocessor (MPU) 14 , driver IC 15 , and memory 16 .
  • the magnetic disk device 1 is connectable to a host 17 .
  • the head 10 includes, as will be described later, a write head 10 W, read head 10 R, and spin torque oscillator (STO) 100 which is a high frequency oscillator.
  • STO spin torque oscillator
  • the R/W channel 12 , HDC 13 , and MPU 14 may be incorporated into a one chip integrated circuit.
  • the magnetic disk 2 includes, for example, a disk-shaped nonmagnetic substrate. On each recording surface of the substrate, there are a soft magnetic layer formed of a soft magnetic material as an underlying layer, and above that, a magnetic recording layer having a magnetic anisotropy in a direction perpendicular to the recording surface, and above that, a protection film layer. A direction to the head 10 is an above direction.
  • the magnetic disk 2 is fixed to the spindle motor (SPM) 3 , and is rotated by the SPM 3 at a certain speed. Note that, instead of a single magnetic disk 2 , there may be several magnetic disk 2 disposed on the SPM 3 .
  • the SPM 3 is driven by drive current supplied from the driver IC 15 (or drive voltage). A data pattern is recorded to/resumed from the magnetic disk 2 by the head 10 .
  • the actuator 4 is disposed rotatably, and the head 10 is supported at its tip.
  • the voice coil motor (VCM) 5 By rotating the actuator 4 with the voice coil motor (VCM) 5 , the head 10 is moved onto a desired track on the magnetic disk 2 to be positioned thereon.
  • the VCM 5 is driven by the drive current (or drive voltage) supplied from the driver IC 15 .
  • the head 10 includes the slider 8 , and the write head 10 W and the read head 10 R formed on the slider 8 (cf. FIG. 2 ). There are several heads 10 corresponding to the magnetic disk 2 . For example, two heads 10 are disposed with respect to the upper surface and the bottom surface of one magnetic disk 2 .
  • the head amplifier IC 11 includes circuits related to drive of the STO 100 and detection of oscillation.
  • the head amplifier IC 11 is disposed between the head 10 and the R/W channel (read/write circuit).
  • the head amplifier IC 11 includes, in the present embodiment, an STO controller 111 , recording coil controller 112 , resume signal detector 113 , and heater controller 114 with a control value storage 114 A.
  • the head amplifier IC 11 executes the drive of the STO 100 and the detection of drive signal, for example.
  • the head amplifier IC 11 supplies a write signal (write current) corresponding to write data supplied from the R/W channel 12 to the write head 10 W.
  • the head amplifier IC 11 amplifies a read signal output from the read head 10 R and transfers the amplified read signal to the R/W channel 12 .
  • the STO controller 111 controls current supplied to the STO 100 of the write head 10 W.
  • the recording coil controller 112 controls recording current supplied to a coil of the write head 10 W corresponding to a write signal.
  • the resume signal detector 113 detects a signal (read data) read by the read head 10 R.
  • the heater controller 114 controls power supply to a heater 28 which will be described later. That is, the heater controller 114 switches on/off of the heater 28 .
  • the heater controller 114 reads a control value set/stored in the control value storage 114 based on a head number or a track, and controls the operation of the heater 28 (described later) based on the read control value.
  • the operation of the heater 28 is controlled based on an output corresponding to a gap detected by a gap sensor (detector) 50 which will be described later, in addition to the control output based on the control value.
  • the R/W channel 12 is a signal processing circuit configured to process signals related to read/write.
  • the R/W channel 12 includes a read channel which executes a signal processing of the read data and a write channel which executes a signal processing of the write data.
  • the R/W channel 12 converts a read signal into digital data, and decodes read data from the digital data.
  • the R/W channel 12 encodes write data transferred from the HDC 13 , and transfers the encoded write data to the head amplifier IC 11 .
  • the HDC 13 controls data write to/data read from the magnetic disk 2 using the head 10 , head amplifier IC 11 , R/W channel 12 , and MPU 14 .
  • the HDC 13 structures interface between the magnetic disk device 1 and the host 17 , and executes transference control of read data and write data. That is, the HDC 13 functions as a host interface controller configured to receive a signal transferred from the host 17 and transfers a signal to the host 17 . When the signal is transferred from the host 17 , the HDC 13 executes an error correction process of data of recording signal read by the head 10 in accordance with the MPU 14 and decoded. Furthermore, the HDC 13 receives commands (write command, read command, and the like) transferred from the host 17 and transfers the received command to the MPU 14 .
  • the MPU 14 is a main controller of the magnetic disk device 1 , and executes a servo control required for controlling of the read/write operation and positioning of the head 10 .
  • the magnetic disk 2 stores positioning information, and the servo control to position the magnetic head 10 to a desired position based on the positioning information read by the read head 10 R.
  • the driver IC 15 controls the drive of the SPM 3 and the VCM 5 in accordance with the control of the MPU 14 .
  • the head 10 is positioned onto a target track on the magnetic disk 2 .
  • the memory 16 includes a volatile memory and a nonvolatile memory.
  • the memory 16 includes a buffer memory which is a DRAM, and a flash memory.
  • the memory 16 stores programs and parameters required for the process of the MPU 14 .
  • FIG. 4 is a cross-sectional view of an example of the structure of the head 10 .
  • FIG. 4 illustrates the head 10 formed as a separate type head including the write head 10 W and the read head 10 R formed at the tip of the slider 8 through a thin film process.
  • the slider 8 includes an air bearing surface (ABS, or head surface) 9 facing the recording surface of the magnetic disk 2 to be floating over the recording surface of the magnetic disk 2 .
  • the write head 10 W writes data to the magnetic disk 2 .
  • the read head 10 R reads data recorded on the magnetic disk 2 .
  • the write head 10 W includes a main magnetic pole 20 , return magnetic pole 21 , nonconductive material 22 , reading magnetic pole 23 , connector 23 B, first recording coil 24 , second recording coil 25 , first terminal 26 , second terminal 27 , and STO 100 .
  • the main magnetic pole 20 , return magnetic pole 21 , and reading magnetic pole 23 are formed of a high permeability material.
  • the main magnetic pole 20 and the return magnetic pole 21 structure a first magnetic core forming a closed magnetic circuit, and the first recording coil 24 is wound onto the first magnetic core.
  • the main magnetic pole 20 and the reading magnetic pole 23 structure a second magnetic core forming a closed magnetic circuit, and the second recording coil 25 is wound onto the second magnetic core.
  • the main magnetic pole 20 generates a recording magnetic field in a direction perpendicular to the recording surface (recording layer) of the magnetic disk 2 .
  • the main magnetic pole 20 is formed to extend substantially perpendicular to the recording surface of the magnetic disk 2 .
  • the tip of the main magnetic pole 20 in the magnetic disk 2 side is tapered toward to the recording surface.
  • the tip of the main magnetic pole 20 is partly exposed to the ABS 9 of the slider 8 .
  • the first terminal 26 is connected to the main magnetic pole 20 for current supply. For example, the first terminal 26 supplies direct current.
  • the return electrode 21 is formed in a substantial L-letter shape such that the tip in the magnetic disk 2 side bends toward the main magnetic pole 20 .
  • the tip of the return magnetic pole 21 faces the tip of the main magnetic pole 20 with a write gap WG therebetween.
  • the return magnetic pole 21 includes a projection at a position apart from the magnetic disk 2 , and the projection is connected to the main magnetic pole 20 via the nonconductive material 22 .
  • the first recording coil 24 is wound onto the periphery of the projection.
  • a second terminal 27 is connected to the return magnetic pole 21 .
  • the second terminal 27 supplies direct current as with the first terminal 26 .
  • the STO 100 is disposed, within the write gap WG, between the tip of the main magnetic pole 20 and the tip of the return magnetic pole 21 .
  • the STO 100 is formed as a substantial cuboid of laminated structure with a magnetic material film and a nonmagnetic material film.
  • the surface formed of the tip surface of the main magnetic pole 20 , tip surface of the return magnetic pole 21 , and STO 100 is exposed to the ABS 9 , and is disposed to face the recording surface of the magnetic disk 2 .
  • the STO 100 is electrically connected to the main magnetic pole 20 and the return magnetic pole 21 via the nonmagnetic conductive layer.
  • a conductive circuit which supplies electricity via the main magnetic pole 20 , STO 100 , and return magnetic pole 21 .
  • the spin in the ferromagnetic material included in the oscillator gains precession because of the magnetic characteristics of electrons.
  • the STO 100 oscillates in a micro waveband alternate signal (high frequency magnetic field) through the precession.
  • the STO 100 is controlled to be turned on/off by the STO controller 111 and the coil controller 112 in accordance with the control of the MPU 14 .
  • the reading magnetic pole 23 is formed of a soft magnetic material.
  • the reading magnetic pole 23 is disposed, with respect to the main magnetic pole 20 , in the opposite side of the return magnetic pole 21 , that is, in the reading side of the main magnetic pole 20 .
  • the reading magnetic pole 23 is formed in a substantial L-letter shape, and the tip thereof is opposed to the tip of the main magnetic pole 20 with a gap therebetween.
  • the upper end of the reading magnetic pole 23 which is apart from the magnetic disk 2 is connected to the main magnetic pole 20 via the connector 23 B formed of a magnetic material.
  • the second recording coil 25 is wound onto the periphery of the connector 23 B.
  • the first recording coil 24 and the second recording coil 25 are wound in the opposite directions.
  • the first recording coil 24 and the second recording coil 25 are connected together via the head amplifier IC 11 in series.
  • the current supply to the first recording coil 24 and the second recording coil 25 is controlled by the recording coil controller 112 . Note that the current supply to the first recording coil 24 and the second recording coil 25 may be controlled separately. When alternate current is supplied to the first recording coil 24 and the second recording coil 25 , the main magnetic pole 20 is excited.
  • the read head 10 R includes a magnetic film 30 having a magnetic resistance effect, and shield films 31 and 32 holding the magnetic film 30 from its trailing side and reading side. The lower end of the magnetic film 30 , and shield films 31 and 32 is exposed on the ABS 9 of the slider 8 .
  • the head 10 includes a heater 28 .
  • the heater 28 is embedded in the slider 8 .
  • the heater 28 is, for example, disposed between the first recording coil 24 and the second recording coil 25 above the main magnetic pole 20 .
  • a second heater may be arranged in a side of the shield film 31 , for example.
  • three or more heaters may be disposed.
  • the heater 28 is connected to the heater controller 114 of the head amplifier IC 11 .
  • a control output based on a control value read from the control value storage 114 A corresponding to a desired head number or track with an output based on a gap detected by a gap sensor 50 which will be described later is output to the heater 28 .
  • the heater 28 With this power supply, the heater 28 is heated, and the slider 8 part in the proximity thereof is heated accordingly.
  • the slider 8 , write head 10 W, and read head 10 R are thermal expanded, and the ABS 9 projects to the recording surface side of the magnetic disk 2 .
  • a floating degree of the head 10 (a distance between the head surface of the write head 10 W and the read head 10 R and the recording surface of the magnetic disk 2 , that is, gap therebetween) can be adjusted by the heater 28 . That is, a gap between the head 10 and the magnetic disk 2 can be adjusted based on a value of the current supplied (voltage applied) to the heater 28 .
  • FIG. 5 is a schematic view illustrating control to maintain a certain gap between the ABS 9 (head surface) and the recording surface of the magnetic disk 2 in the magnetic disk device 1 .
  • FIG. 5 illustrates the slider 8 and the head 10 disposed on the tip of the slider 8 , and the head 10 is depicted in an enlarged manner in the part pointed by the arrow.
  • a gap sensor 50 is disposed in the proximity of the heater 28 .
  • FIG. 5 illustrates a state where the power is supplied to the heater 28 and the ABS 9 (the write head 10 W and the read head 10 R) is projected to the recording surface 2 A of the magnetic disk 2 .
  • the measurement of the distance (that is, gap) between the ABS 9 and the recording surface 2 A of the magnetic disk 2 by the gap sensor 50 is performed as follows.
  • the gap sensor 50 is formed of a material having a high temperature coefficient in order to generate heat by supplying constant current to the gap sensor 50 during write/read.
  • the heater 28 is expanded, and the ABS 9 approaches the recording surface 2 A of the magnetic disk 2 .
  • the gap sensor 50 approaches the recording surface 2 A of the magnetic disk 2 accordingly.
  • the heat of the gap sensor 50 escapes to the magnetic disk 2 .
  • the gap sensor 50 When the heat escapes, a resistance value of the gap sensor 50 decreases, and a change in the gap between the magnetic disk 2 and the recording surface 2 A is measured using the change in the resistance value.
  • the gap sensor 50 is not limited to a type by which the resistance value is measured, and for example, may be a type by which a capacitance between the ABS 9 and the recording surface 2 A of the magnetic disk 2 , in which a change in the gap between the ABS 9 and the recording surface 2 A of the magnetic disk 2 is measured based on a change in the capacitance.
  • FIG. 6 illustrates an example of the output of the gap sensor 50 in a case where there is changing in the floating degree of the head 10 .
  • FIG. 6(A) illustrates, as in FIG. 2 , an example of changes of gap between the ABS 9 and the recording surface 2 A of the magnetic disk 2 during one rotation of the magnetic disk 2 .
  • FIG. 6(B) illustrates an example of an output of the gap sensor 50 (graph g 14 ) during one rotation of the magnetic disk 2 . Comparing graph g 12 indicative of a gap between the write head 10 W and the recording surface 2 A and graph g 14 indicative of an output of the gap sensor, the waveforms are apparently similar.
  • a gain is added to the control value set in the heater 28 , and thus, the expansion of the heater 28 is suitably controlled, and a gap between the ABS (head surface) 9 and the recording surface 2 A of the magnetic disk 2 is maintained.
  • FIG. 7 illustrates an example of the structure of a circuit which controls a gap between the ABS 9 and the recording surface 2 A of the magnetic disk 2 .
  • the circuit is mounted on the head amplifier IC 11 ; however, the circuit may be disposed in other controller. That is, the circuit should be disposed optionally in the magnetic disk device 1 .
  • the output from the gap sensor 50 is input in an amplifier 53 via terminals 51 and 52 .
  • the amplifier 53 amplifies the output from the gap sensor 50 .
  • the amplifier 53 amplifies the output of the gap sensor 50 to an integer multiple, for example.
  • the amplified output passes a high pass filter (HPF) 54 and a low pass filter (LPH) 55 .
  • HPF high pass filter
  • LPH low pass filter
  • the output of the gap sensor 50 is input in a gain adjustor 56 .
  • the gain adjustor 56 adjusts the gain of the output of the gap sensor 50 .
  • a gain by which the output change of the gap sensor 50 is minimized is derived by monitoring the output of the gap sensor 50 and changing the value of the gain adjustor 56 , and is set in the gain adjustor 56 .
  • control value 57 of the heater 28 is read from the control value storage 114 A corresponding to a number of the head 10 and a positioned track, for example.
  • the read control value of the heater 28 is subjected to the digital/analogue conversion in the digital analogue converter (DAC) 58 , and then, is amplified by the amplifier 59 .
  • DAC digital analogue converter
  • the adjusted gain from the gain adjuster 56 that is, the output of the gap sensor 50 is added, and the control value with the output added is output as a control output to control the expansion of the heater 28 from an amplifier 60 .
  • the circuit mounted on the head amplifier IC 11 the output of the gap sensor 50 is monitored, and the gain of the gain adjustor 56 is carried corresponding to the output of the gap sensor 50 . Then, the gain by which the output change of the gap sensor becomes minimum is added to the control output read from the control value storage 114 A in order to minimize the gap between the ABS 9 and the recording surface 2 A of the magnetic disk 2 in read/write operation.
  • FIG. 8 illustrates an example of a result of adjustment of the control output value of the heater 28 using the circuit of FIG. 7 .
  • FIG. 8(A) illustrates, as in FIG. 2 , an example of changes of the gap with respect to the magnetic disk 2 during one rotation thereof in a case where a control output value of the heater 28 of the present embodiment is not adjusted.
  • FIG. 8(B) illustrates an example of changes of the gap with respect to the magnetic disk 2 during one rotation thereof in a case where a control output value of the heater 28 of the present embodiment is adjusted.
  • FIG. 8(B) illustrates graph g 21 indicative of the recording surface 2 A of the magnetic disk 2 , graph g 22 indicative of a distance between the write head 10 W and the recording surface 2 A, and graph g 23 indicative of a constant gap.
  • a distance D 21 indicative of a minimum gap between graphs g 21 and g 22 and a distance D 22 indicative of an axial runout are shown.
  • a distance between graph g 22 indicative of a distance between the write head 10 W and the recording surface 2 A and graph g 23 indicative of a constant gap is substantially equal.
  • the gap between the ABS 9 and the recording surface 2 A of the magnetic disk 2 becomes short while the minimum gap D 21 is maintained, and the magnetic disk device 1 can improve the quality of the write/read.
  • the magnetic disk device 1 can further improve the track recording density. Such an effect can be achieved in the read operation as well.
  • an analogue circuit in which a gain derived based on the output of the gap sensor 50 is added to the control output of the heater 28 is used, and in a second embodiment, a digital circuit is used instead.
  • FIG. 9 illustrates an example of the structure of a circuit which controls a gap between an ABS (head surface) 9 and a recording surface 2 A of a magnetic disk 2 .
  • the circuit is mounted on a head amplifier IC 11 ; however, the circuit may be disposed in other controller as in the first embodiment.
  • Output of the gap sensor 50 is input into an amplifier 53 via terminals 51 and 52 , and output of the amplifier 53 passes a high pass filter (HPF) 54 and low pass filter (LPH) 55 to be input in a gain adjustor 56 as in the first embodiment.
  • HPF high pass filter
  • LPH low pass filter
  • the output of the gain adjustor 56 is input into the analogue-digital converter (ADC) 61 .
  • the digital output of the ADC 61 is added to a digital output of a heater control value 57 by an adder 62 .
  • the digital value of the heater control value 57 with the output of the gap sensor 50 added is converted into an analogue output in the digital-analogue converter (DAC) 58 , and is input into an amplifier 59 .
  • the converted control output is output from the amplifier 59 as a control output for controlling expansion of the heater 28 .
  • a timing signal S 1 is a signal to match a time of adding an output of the heater control value 57 and a gain corresponding to an output of the gap sensor 50 by the adder 62 .
  • the control of matching the time using the timing signal S 2 is performed, for example, per one servo frame or per every two servo frame.
  • a process of averaging a digital value based on the output of the gap sensor 50 may be performed, and the averaged digital value may be input in the adder 62 during an update interval of the heater control value 57 .
  • the circuit structured as above can achieve a similar effect as in the first embodiment.
  • the output value of the gap sensor 50 may be subjected to a masking process in the write operation. Whether or not it is in the write operation will be determined, for example, based on a write gate turned on.
  • the write gate is an instruction to write data to the magnetic disk 2
  • on/off of the write gate is, for example, transferred to the head amplifier IC 11 from the R/W channel 12 .
  • a gain (adjustment value) based on the output of the gap sensor 50 is added to the control value of the heater 28 in a dynamic manner during the write operation, and the operation of the heater 28 is controlled, and in a third embodiment, the magnetic disk device 1 stores a gain to be added to a control value in a register, and adds the gain stored in the resister to a control value of the heater 28 to control the heater 28 .
  • FIG. 10 illustrates an example of the structure of a circuit to control an ABS (head surface) 9 and a recording surface 2 A of a magnetic disk 2 .
  • the circuit is mounted on a head amplifier IC 11 ; however, the circuit may be disposed in other controller as in the first and second embodiments.
  • a gain added to the control value of the heater 28 is stored in a register 115 A as a gain per one servo frame or per every two servo frame during one rotation of the magnetic disk 2 , for example.
  • the gain stored in the register 115 A is preliminarily measured using the gap sensor 50 or the like and is stored in the register 115 A. Then, at a time of reading the servo data from the magnetic disk 2 by the read head 10 R, the gain is read from the register 115 A corresponding to the head 10 and a track, for example, in synchronization with turning on of the servo gate.
  • the gain read is added, during the write operation, to a control value 57 of a heater 28 read from a control value storage 114 A by an adder 63 , and the added value is converted by a digital-analogue converter (DAC) 58 . Then, the converted control output is output by the amplifier 59 as a control output for controlling expansion of the heater 28 .
  • DAC digital-analogue converter
  • the number of register 115 A will be, if the number of servo frames is six hundreds during one rotation of the magnetic disk 2 , six hundreds necessary while the heater 28 is controlled per servo frame, and three hundreds necessary while the heater 28 is controlled per every two servo frame. With such a structure, a similar effect as in the above embodiments can be achieved as well. Furthermore, a process to add an output from the gap sensor 50 in the write/read operation can be omitted because a gain is preliminarily stored in the register 115 A, and a gap can be adjusted even if there is an abnormality in the circuit including the gap sensor 50 . Note that which of the radius positions of the magnetic disk 2 is used to obtain a gain of one rotation may be set optionally.
  • a gain of one rotation from an optional one radius position of the magnetic disk 2 is stored in a register; however, several radius positions may be set in a radius direction, for example, and a gain per certain servo frame number of one rotation may be stored in the register per radius position.
  • FIG. 11 illustrates an example of the structure of a register in a case where several radius positions are set.
  • three radius positions are set as the several radius positions, and a gain per certain servo frame number is stored in the register from the three radius positions.
  • certain radius positions of inner track, middle track, and outer track of the magnetic disk 2 are set, and a register 115 B to store a gain corresponding to the three radius positions is provided.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Adjustment Of The Magnetic Head Position Track Following On Tapes (AREA)
  • Magnetic Heads (AREA)
  • Supporting Of Heads In Record-Carrier Devices (AREA)
  • Digital Magnetic Recording (AREA)
US16/939,447 2019-12-24 2020-07-27 Magnetic disk device Active US11074936B2 (en)

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